FIG. 1 depicts a conventional method 10 for defining the stripe height of a magnetoresistive structure using a conventional undercut bi-layer mask. FIGS. 2-3 depict a conventional magnetoresistive device 50, such as a read transducer, during fabrication using the conventional method 10. Referring to FIGS. 1-3, the layers of the magnetoresistive structure stack are provided, via step 12. Typically, step 12 includes sputtering or otherwise depositing the layers for a spin valve or other analogous giant magnetoresistive (GMR) element. A bi-layer mask is provided on the device, via step 14. FIG. 2 depicts a side view of the conventional transducer 50 after step 14 is performed. Thus, the conventional transducer 50 includes a magnetoresistive stack 54 of the magnetoresistive structure layers formed on a substrate 52, which is typically a shield. On the magnetoresistive stack 54 is a bi-layer mask 56 that includes a polydimethylglutarimide (PMGI) layer 60 and a photoresist layer 58. The bi-layer mask 56 has an undercut 62 at the edges of the mask 56. The undercut 62 is formed due to shrinkage of the PMGI layer 60 after the layer is fabricated.
The magnetic structure is defined, via step 16. Typically, this is accomplished by ion milling the magnetoresistive stack 54. Consequently, portions of the magnetoresistive stack 54 exposed by the bi-layer mask 56 are removed. Step 16 defines the stripe height, or maximum distance from the air-bearing surface (ABS), of the magnetoresistive structure. Note that although the ABS is shown in FIGS. 2-3, this is actually just a reference location. The ABS is typically defined in subsequent processing steps, for example via lapping. In addition, the magnetoresistive structure may be defined in the track width direction, which is out of the plane of the page in FIG. 2. The region behind the magnetoresistive structure is refilled with an insulator, such as alumina, via step 18. Also in step 18, other structures may be provided on either side of the magnetic element in the track width direction. For example, hard bias structures (not shown) may be provided at the sides of the magnetic structure. FIG. 3 depicts the conventional magnetic transducer 50 after step 18 is performed. The magnetoresistive structure 54′ has been defined in step 16. Redeposition 64 of the magnetoresistive stack 54 materials results from step 16 and resides on the side of the photoresist portion 58. Aluminum oxide 66 and 68 from step 18 resides behind and on the magnetoresistive structure 54 and on the photoresist 58, respectively.
The bi-layer mask 56 is removed, via step 20. Because of the shape of the mask 56, redeposition 64 generated by step 16 and the insulator 68 provided in step 18 generally do not fill the undercut 62. This is shown in FIG. 3. As a result, solvents that attack the PMGI 60 may be used. A lift-off may, therefore, be performed in step 20 to remove the mask 56. Fabrication of the conventional magnetic transducer 50 may then be completed, via step 22. For example, a shield and/or other structures may be provided.
Although the conventional method 10 functions at lower densities, issues arise for higher densities. The bottom, PMGI layer 60 of the bi-layer mask 56 has a smaller length, or critical dimension, than the upper photoresist layer 58. Consequently, as discussed above, the bi-layer mask 64 has an undercut 62. The typical length of the undercut 62 is on the order of forty to fifty nanometers and is subject to large variations. In addition, the stripe height h, is desired to be reduced for higher density recording. For example, the stripe height may be desired to be one hundred nanometers or less. The variations in the undercut 62 are thus a significant fraction of the length of the entire structure 54′ being formed. As a result, the magnetoresistive structure 54′ may exhibit large variations in the stripe height. Such variations are generally undesirable.
In addition, the bi-layer mask 56 may collapse. The photoresist layer 58 may thus close the undercut 62. Consequently, solvent used in the liftoff process of step 20 may not be able to reach the PMGI 60. The mask 56 thus may become difficult to remove. In addition, a portion of the aluminum oxide 66 resides on the magnetoresistive structure 54′. This and other redeposition on the surface of the conventional magnetoresistive structure 54′ may result in variations in the shield-to-shield spacing for the conventional magnetic transducer 50. Such variations are generally undesirable.
Accordingly, what is needed is an improved system and method for providing a magnetoresistive device, particularly which may be suitable for higher recording densities.